Translation:I work out every single day.
It is not a good idea to work out every single day. The body needs a day every two or three day to recover and build up muscle mass. Just saying!
Exercise includes a bunch of simple activities, like walking, that are very good for you and can be done everyday.
你是对的! You're right that there are many non-strenuous exercises that we can do daily. But, in this case, I wonder if 运动 would be a more appropriate word to use than 锻炼?
If you translate 每天, it refers to "every day". Because of 都 (numerical inclusive), there is no need to specify greater cardinal numbers (2, 3, ...). The point is to assume that the action is done every past period of time. Otherwise, the meaning of the sentence is vague, which then assumes that the event did not occur in some of all days.
Likewise, 都 should be included for "subtime" within a period of time, for instance,
Otherwise, the number is specified there, such as 每两天 (every two days). If this were to be included for the given translation, then we have
'I work out every two days.
However, because of 都, which makes every single day inclusive, this makes the sentence sound too redundant. Thus, the most accurate answer is
If 都 were to be excluded, then you are expressing that event occurred for some "pairs of days" (much like if you were to express 我每天锻炼).
都 is used for emphasis.
The sentences with and without 都 have similar, but colloquially different meanings.